This application pertains to the field of separating and recovering metal values from a waste stream. In particular, the waste stream is that which is generated during the course of depositing metals onto a substrate such as electrolytic deposition of metals onto a substrate or the electroless deposition of metals onto a substrate. Due to substantial environmental concerns of metals that are present in waste streams, it is deemed desirable to recover such metals and to reuse them in an economically designed process.
Regenerating spent electrolytic baths containing chromium by oxidizing undesirable ions, separating formed oxides and concentrating the solution is discussed in Japanese patent application No. 123033, filed Oct. 31, 1973 and published June 16, 1975 as Japanese publication No. 50/72834. A rinsing waste solution from hard chromium plating containing chromium (VI) and iron ions with a pH of 2.3 was subjected to ultrasound source (1.35 MHz 30-W). An increase in chromium (VI) was obtained with a decrease in iron ions.
Japanese patent application No. 74/101528 filed Sept. 3, 1974 and published Mar. 10, 1976 discloses chromate in a waste water solution which is reduced and precipitated as chromium hydroxide. An alkali is added to the chromium hydroxide and the mixture is treated ultrasonically under oxygen atmosphere. The chromic acid is obtained by passing the resulting solution through a hydrogen ion type ion exchange resin.
The oxidation of chromium (III) ions by manganese dioxides is discussed in The Journal of Inorganic Nuclear Chemistry, 1977, Vol. 39 pages 1081-1084, Basak et al.
U.S. Pat. No. 3,245,892 teaches a method for ultrasonically activating chemical reactions requiring the presence of a catalyst.
U.S. Pat. No. 4,369,100 describes a method for enhancing chemical reactions in a constantly flowing stream of liquid which contains air as an oxidant which in turn is subjected to ultrasonic cavitation.
U.S. Pat. No. 4,731,166 teaches a method of producing an adherent smooth depositive chromium on a ferrous substrate. Ultrasonic energy is used to remove nodular ferrous nodules from the substrate prior to electroplating chromium thereon.
U.S. Pat. No. 4,755,270 describes a method of processing waste solutions containing metal salts or complex involving applying ultrasonic vibrations to a container in which the solution is placed to mist the water and subsequently capturing the water vapor discharge from the container, exhausting the vapor through a filter to capture any heavy metals in the water vapor.
The references do not suggest a technique for commencing with a waste stream containing a variety of metal values, and subjecting the waste stream to a multiplicity of processing steps to separate and recover the metal values present in the waste stream. The references likewise do not suggest the obtaining of these metal values without undesirable waste streams which likewise need to processed so as not to generate significant environmental concerns.